Marine engine thrust augmenter

ABSTRACT

The thrust augmenter may be of a generally circular open ended cylindrical from having an open side portion. The thrust augmenter may be attached about a propeller axis to partially enclose the propeller. The attachment may be such that the open side portion may be positioned at the lower portion of the propeller. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

BACKGROUND OF THE INVENTION

[0001] This invention relates to devices for outboard engines used with watercraft that improve the thrust of the engine and lift of the watercraft. The new thrust augmentation device partially encloses the propeller of an outboard engine about the propeller shaft axis.

[0002] Propellers of marine engines have been enclosed by open cylinder devices to shield the propeller blades from damage should the engine in the area of the propeller impact foreign objects. Such cylindrical enclosing devices may not improve the thrust of the engine, but push power may be increased for large slow RPM engines (propeller size 3 feet to 4 feet) without any improved watercraft lift force.

SUMMARY OF THE INVENTION

[0003] The present invention is directed to devices for augmentation of the thrust of outboard marine engines. A thrust augmenter may be of a general circular open ended cylindrical from having an open side portion. The thrust augmenter may be attached about a propeller axis to partially enclose the propeller. The attachment may be such that the open portion may be positioned at the lower portion of the propeller to increase lift force to carry the watercraft to plane on the water at reduced engine RPM.

[0004] These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 illustrates a perspective view of the thrust augmenter attached to an outboard marine engine;

[0006]FIG. 2 illustrates an end elevation view of the thrust augmenter attached to an outboard marine engine according to an embodiment of the invention;

[0007]FIG. 3 illustrates a perspective view of the thrust augmenter according to an embodiment of the invention.

DETAILED DESCRIPTION

[0008] The following detailed description is the best currently contemplated modes for carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention.

[0009] Referring to FIGS. 1 and 2, an outboard marine engine propeller and drive shaft assembly 10 may have a propeller 12 attached to a propeller shaft 14. The propeller 12 may be positioned rearward of a fin 16. The fin 16 may have a lower unit 18 with a horizontal plane element 20. This may be the normal configuration of the lower underwater structure of an outboard marine engine. The thrust of the engine is primarily determined by engine power, drive mechanism, and propeller configuration. For example, changes in RPM may change thrust.

[0010] The thrust augmenter 30 may be a generally circular open ended partial cylinder. It may be formed of two augmenter elements 32, 34, as may be viewed in FIG. 3. The thrust augmenter 30 may be attached to the lower unit 18 or to a horizontal plane element 20 by bolts 36, or other fastener methods. The aft aperture (not shown) for the bolt 36 may be in the form of a slot to allow positioning of the thrust augmenter axis of the propeller shaft 14.

[0011] The propeller 12 may be partially enclosed about the propeller shaft 14 axis by the thrust augmenter 30 to provide the thrust augmentation and lift force effect. Full enclosure of the propeller 12 has been found not to provide the advantage of increased thrust and acceleration, or savings in use of fuel for high speed outboard engines.

[0012] The side wall 40 may enclose the upper and side areas of the propeller 12 in an approximate semicircular cross section and be spaced apart from the propeller 12 outer edge approximately 1 inch. The illustrated embodiment is semicircular in form with the side walls 40 terminating approximately at the horizontal axis of the propeller shaft 14 as may be viewed in FIG. 2. A thrust augmenter 30 may also be less than semicircular in form. A single element thrust augmenter 30 may also be used.

[0013] A taper on forward edge 42 of the side wall 40 may be used to deflect debris in the water. The taper may cause the sidewall upper portion 44 to be longer than the bottom edge 46 of the sidewall 40.

[0014] While the invention has been particularly shown and described with respect to the illustrated and preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention. 

I claim:
 1. A device to augment the thrust of an outboard marine engine comprising: a thrust augmenter of generally circular open ended cylindrical form having an open side portion therein and attachable about a propeller shaft axis to partially enclose a propeller such that said open side portion is positioned at the lower portion of said propeller.
 2. The device as in claim 1 wherein a side wall of said thrust augmenter is terminated approximately at a propeller shaft horizontal axis.
 3. The device as in claim 1 wherein a side wall of said thrust augmenter is spaced apart approximately one inch from a propeller outer edge.
 4. The device as in claim 1 wherein said thrust augmenter is formed of a first augmenter element and a second augmenter element.
 5. The device as in claim 1 wherein a side wall of said thrust augmenter at a forward edge is tapered from an upper portion to a bottom edge.
 6. The device as in claim 1 wherein said thrust augmenter is attachable to a horizontal plane element of a lower unit.
 7. The device as in claim 1 wherein said thrust augmenter is attached by bolts.
 8. A device to augment the thrust of an outboard marine engine comprising: a thrust augmenter of generally open ended cylindrical form having an open side portion therein attachable to said outboard marine engine wherein a side wall of said thrust augmenter is terminated approximately at a propeller shaft horizontal axis of said outboard marine engine.
 9. The device as in claim 8 wherein a side wall of said thrust augmenter is spaced apart approximately one inch from a propeller outer edge.
 10. The device as in claim 8 wherein said thrust augmenter is formed of a first augmenter element and a second augmenter element.
 11. The device as in claim 8 wherein a side wall of said thrust augmenter at a forward edge is tapered from an upper portion to a bottom edge.
 12. The device as in claim 8 wherein said thrust augmenter is attachable to a horizontal plane element of a lower unit.
 13. The device as in claim 8 wherein said thrust augmenter is attached by bolts.
 14. A device to augment the thrust of an outboard marine engine comprising: a thrust augmenter of generally open ended cylindrical form having an open side portion therein attachable to said outboard marine engine wherein a side wall of said thrust augmenter is terminated approximately at a propeller shaft horizontal axis of said outboard marine engine; and said side wall is spaced apart approximately one inch from a propeller outer edge. 